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. 2024 Jun 7;128(24):5823–5839. doi: 10.1021/acs.jpcb.4c01237

Table 2. Energy Barriers Calculated for H Atom Transfer between Cys493 and Gly829 in the Holoenzyme (E:S or E:P) with Either Bound Substrates (TSES) or Product (TSEP) or in the Apoenzyme with an Empty Active Site (apo)a.

Attack   H transfer from Cys to GlyradΔ(E+thermal) [kJ/mol]
 Attack   H transfer from Gly to CysradΔ (E+Thermal) [kJ/mol]
    re H GlyH• re D GlyH• re H GlyD• re D GlyD•     R-H GlyH2 R-D R-GlyHD R-H S-GlyDH R-D GlyD2
E:S re E:S 0.0 0.0 0.0 0.0 E:S R-trans. IES 0.0 0.0 0.0 0.0
TSES 40.4 43.2 39.8 42.6 TSES 72.2 77.4 72.4 77.7
IES –31.7 –34.2 –32.6 –35.2 E:S 31.7 34.2 32.6 35.2
E:P re E:P 0.0 0.0 0.0 0.0 E:P R-trans. IEP 0.0 0.0 0.0 0.0
TSEP 38.8 41.5 38.1 40.8 TSEP 72.5 77.7 72.7 78.0
IEP –33.7 –36.2 –34.6 –37.2 E:P 33.7 36.2 34.6 37.2
apo re Eapo 0 0 0 0 apo R-trans. Iapo 0 0 0 0
TSapo 107.0 109.8 106.2 109.0 TSapo 99.8 105.0 99.7 104.9
Iapo 7.2 4.8 6.5 4.0 Eapo –7.2 –4.8 –6.5 –4.0
    si H Gly H• si D GlyH• si H GlyD• si D GlyD•     S-H GlyH2 S-D S-GlyDH S-H R-GlyHD S-D GlyD2
E:S si E:S 0.0 0.0 0.0 0.0 E:S S-trans. IES 0.0 0.0 0.0 0.0
TSES 62.2 64.8 61.5 64.2 TSES 95.8 101.0 96.1 101.4
IES –33.7 –36.2 –34.6 –37.2 E:S 33.7 36.2 34.6 37.2
E:P si E:P 0.0 0.0 0.0 0.0 E:P S-trans. IEP 0.0 0.0 0.0 0.0
TSEP 61.9 67.8 61.2 67.1 TSEP 96.4 104.7 96.6 105.0
IEP –34.4 –36.9 –35.4 –37.9 E:P 34.4 36.9 35.4 37.9
apo si Eapo 0 0 0 0 apo S-trans. Iapo 0 0 0 0
TSapo 80.6 80.1 83.1 82.7 TSapo 2.3 2.4 7.4 7.6
Iapo 78.3 77.8 75.7 75.1 Eapo –78.3 –77.8 –75.7 –75.1
a

The electronic energies were corrected with thermal energy calculated for models with protium-only substituted Gly (re-/si-H GlyH), with either enantiomer of monodeuterated Gly assuming transfer of either its deuterium (re/si-D GlyH•) or protium-substituent (re/si-H GlyD•), and with deuterium substituting both H atoms of Gly (re/si D GlyD•). For readers’ convenience, the barriers associated with the respective reverse processes, i.e., transfer of H/D atoms from Gly to radical Cys are provided in the right column (R/S-H or D transfers). Note that the R- and S-enantiomers of monodeutered Gly are also represented as GlyHD and GlyDH, respectively, to aid the comprehension of Figure 6.